1. Field of the Invention
The invention relates to a mold assembly capable of molding an expansion molded body (such as a vehicle seat cushion).
2. Description of the Related Art
Japanese Patent Application Publication No. 2005-153293 (JP-A-2005-153293) describes one such known mold assembly. This mold assembly includes a first die and a second die that is able to close together with the first die such that a cavity is formed between the first die and the second die. This cavity is a molding space that follows the contour (i.e., the exterior shape) of the expansion molded body. When the second die is closed together with the first die, a sealed cavity is formed. Then foam raw material is expanded inside the cavity. Gas (i.e., high pressure air) remaining in the cavity at this time may adversely affect the expansion molded body.
The mold assembly described in JP-A-2005-153293 has a structure (i.e., a first concave portion and a second concave portion) for venting the gas inside the cavity (hereinafter also referred to as “degassing”). The first concave portion is a cutout portion (that is rectangular) provided on the die closing surface of the lower die. A plurality of these first concave portions is formed around the cavity. Also, the second concave portion is a cutout portion (that is groove-shaped) provided on the peripheral edge of the lower die, and is formed around the entire circumference of the cavity. With this related art, gas inside the cavity escapes to the first concave portion and the second concave portion, so problems (such as flash and underfill) with the expansion molded body due to poor degassing are able to be minimized. Incidentally, with this related art, the degassing structure (i.e., both concave portions) is formed directly on the lower die and the like, so the structure of the mold assembly itself tends to be complicated. Also, with the related art, the mold assembly itself must be replaced or repaired when the concave portions are damaged or during maintenance. Therefore, when considering the manufacturing cost and the like of the mold assembly, the structure of the related art is not a structure that can simply be employed without much thought.